What you fail to realize is the lower the price gets, the easier it is to buy the market up.  Let's say there are 100,000 coins sitting on exchanges ready to be dumped at market price.  (Yes, silly, but let's look at this extreme case.)  If I jump in at $100 per coin with a limit order, I can absorb the entirety of the market dump all by myself with just $10 million, and end up 100,000 coins wealthier with a market that has no more ammunition to sell.